Light emitting device and method for manufacturing the same

ABSTRACT

An object of the present invention is to realize a light emitting device having low power consumption and high stability, in addition to improve extraction efficiency of light generated in a light emitting element. At least an interlayer insulating film (including a planarizing film), an anode, and a bank covering an edge portion of the anode contain-chemically and physically stable silicon oxide, or are made of a material containing silicon oxide as its main component in order to accomplish a light emitting device having high stability. Generation of heat in a light emitting panel can be suppressed in addition to increase in efficiency (luminance/current) of a light emitting panel according to the structure of the present invention. Consequently, synergistic effect on reliability of a light emitting device is obtained.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device having a circuitcomposed of a thin film transistor (hereinafter referred to as a TFT),and to a method for manufacturing the same. For example, the inventionrelates to an electronic device which mounts a light emitting displaydevice having a TFT and an organic light emitting element as itscomponent.

In this specification, the term “semiconductor device” refers to adevice in general that utilizes semiconductor characteristics tofunction, and electro-optical devices, semiconductor circuits, andelectronic devices are all included in the semiconductor device.

2. Related Art

In these years, research on a light emitting device having an EL elementas a self-luminous light emitting element is activated. The lightemitting device is also referred to as an organic EL display or anorganic light emitting diode. Since these light emitting devices havecharacteristics such as high response speed that is suitable for moviedisplay, low voltage, and low power consumption driving, they attractsan attention for a next generation display including new generation'scellular phone and personal digital assistant (PDA).

An EL element using a layer containing an organic compound as a lightemitting layer has a structure in which a layer containing an organiccompound (hereinafter referred to as an EL layer) is interposed betweenan anode and a cathode. Electro luminescence is generated in the ELlayer by applying an electric field to the anode and the cathode.Luminescence obtained from the EL element includes luminescencegenerated in returning to a ground state from a singlet excited state(fluorescence) and luminescence generated in returning to a ground statefrom a triplet excited state (phosphorescence).

However, sufficient luminance is not obtained in a conventional lightemitting element using a layer containing an organic compound as a lightemitting layer.

Light generated in an EL layer is extracted, regarding an anode side ora cathode side as a display surface. On this occasion, light is partlyreflected at an interface among different material layers while passingthrough various material layers and a substrate. As a result, there is aproblem that initial emission of light to be transmitted to outside ofan element is reduced by several tens percent and luminance is kept low.

Thus, Reference 1 and Reference 2 by the present applicant propose anelement structure for improving light extraction efficiency (Reference1: Japanese Patent Laid-Open No. 2002-352950, and Reference 2: JapanesePatent Laid-Open No. 2002-229482).

Since luminous efficiency is low in the conventional light emittingelement using a layer containing an organic compound as a light emittingelement, the amount of current for obtaining desired luminance increasesand power consumption also increases. Increase in power consumptiongreatly affects an element life, typically, shortens a half-life time ofluminance. Therefore, the conventional light emitting element using alayer containing an organic compound has a problem that needs to besolved regarding element stability.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide a light emittingdevice having high luminance with high luminous efficiency (lightextraction efficiency), low power consumption, and high stability.

According to the present invention, at least an interlayer insulatingfilm (including a planarizing film), an anode, and a bank covering anedge portion of the anode include chemically and physically stablesilicon oxide, or they are made of a material containing silicon oxideas its main component in order to accomplish a light emitting devicehaving high stability.

Specifically, it is preferable to use a highly thermostable planarizingfilm obtained by application as an interlayer insulating film and abank. An application film using a material in which a skeletal structureis configured by a bond of silicon (Si) and oxygen (O), and whichcontains at least one kind of hydrogen, fluorine, an alkyl group, andaromatic hydrocarbon as a substituent is used as a material of theinterlayer insulating film and the bank. A baked film can be referred toas a SiOx film including an alkyl group. The SiOx film including analkyl group has higher light transmitting property than that of anacrylic resin, and can withstand heat treatment of 300° C. or more.

According to the present invention, as for a method for forming aninterlayer insulating film and a bank by application, thinner pre-wettreatment is performed to improve wettability after performing washingwith purified water. Then, a liquid material referred to as varnish inwhich a low molecular weight component (a precursor) having a bond ofsilicon (Si) and oxygen (O) is dissolved into a solvent is applied overthe substrate by spin coating or the like. Thereafter, a thin film canbe obtained by proceeding volatilization (evaporation) of the solventand cross-linking reaction of the low molecular weight component byheating the varnish together with the substrate. Then, an applicationfilm on the periphery of an end face of the substrate over which theapplication film is formed is removed. In the case of forming the bank,the application film may be patterned to have a desired shape. Inaddition, a film thickness is controlled by the number of spin rotation,rotational time, and concentration and viscosity of the varnish.

Manufacturing costs can be reduced by using the same material for theinterlayer insulating film and the bank. In addition, cost reduction canbe achieved by commonality of an apparatus such as an application filmformation apparatus or an etching apparatus.

Generally, ITO (indium tin oxide) is used for an anode in an EL elementusing a layer containing an organic compound as a light emitting layer.However, ITO has a high refractive index of approximately 2. Therefore,indium tin oxide containing silicon oxide (hereinafter referred to as“ITSO”) is used as an anode in the present invention. ITSO is notcrystallized even by baking, unlike in the case of ITO, and it remainsamorphous. Therefore, ITSO is suitable for an anode of a light emittingelement since it has higher planarity than that of ITO and is hard tocause a short circuit with a cathode even when a layer containing anorganic compound is thin. In addition, a refractive index of ITSO to bean anode is changed by making ITSO contain silicon oxide having arefractive index of approximately 1.46.

Additionally, efficiency (luminance/current) of a light emitting panelusing ITSO as an anode is 1.5 times higher than that of a light emittingpanel using ITO as an anode, as shown in FIG. 6. FIG. 6 shows comparisonin an active matrix light emitting panel using a TFT. Current used forcalculating efficiency corresponds to the total current value that isinputted to a panel.

As shown in FIGS. 12A and 12B, generation of heat is suppressed in alight emitting panel (corresponding to a sample B in FIGS. 12A and 12B)which uses a highly thermostable planarizing film using ITSO as an anodeand being obtained by application as an interlayer insulating film.Consequently, reliability of a light emitting device is improved.

Namely, generation of heat in a light emitting panel can be suppressedin addition to increase in efficiency (luminance/current) of a lightemitting panel according to the structure of the present invention.Consequently, synergistic effect on reliability of a light emittingdevice is obtained.

An electroluminescent device according to the present inventionincreases luminous efficiency by making a laminate through which lightgenerated in a light emitting layer passes when it is transmitted tooutside of a substrate with a highly light transmitting material and bysuppressing reflection among layers having different refraction indexes.Specifically, it is effective to set a refractive index or a filmthickness of an interlayer insulating film through which light passes inthe case of an active matrix light emitting device using a TFT, since alaminate of a plurality of material layers is used as the interlayerinsulating film. In the present invention, a refractive index or a filmthickness of each layer is determined within an adjustable range inaccordance with Snell's law, and light reflection at an interface of thelayer is suppressed. The Snell's law means that, assuming that lightenters a film having a refractive index of n_(j) at an angle of θ_(i)from a film having a refractive index of n_(i) and is transmitted at anangle of θ_(j) (n_(i)·sin θ_(i)=n_(j)·sin θ_(j)), all rays of light arereflected through a path symmetrical to a normal line in the case ofexceeding a value of θ_(j) (critical angle) under a total reflectioncondition (θj=90′ in the Snell's law).

In addition, light emitted from a light emitting element is reflected ordiffused in various directions and is absorbed by various portions(material layer). In the present invention, a portion through whichemitted light does not pass when it is transmitted to outside of asubstrate, for example, a bank is made of a material having hightransmittance and absorption of light in the portion is suppressed.Accordingly, luminous efficiency is increased.

A structure of the present invention disclosed in this specification isa light emitting device comprising a plurality of light emittingelements having a cathode, a layer containing an organic compound, andan anode, wherein a highly thermostable planarizing: film containingSiOx is formed over a substrate having an insulating surface, an anodecontaining SiOx and a bank containing SiOx covering an edge portion ofthe anode are formed over the highly thermostable planarizing film, alayer containing an organic compound is formed over the anode, and acathode is formed over the layer containing an organic compound.

In the above structure, the highly thermostable planarizing film and thebank are made of the same material, and are SiOx films including analkyl group. In addition, in the above structure, the anode is indiumtin oxide containing SiOx. Further, a TFT using the highly thermostableplanarizing film containing SiOx as an interlayer insulating film iselectrically connected to the anode.

Another structure of the present invention is a light emitting devicecomprising a plurality of light emitting elements having a cathode, alayer containing an organic compound, and an anode, wherein lightemitted from a light emitting element passes through an anode containingSiOx, a highly thermostable planarizing film containing SiOx, and asubstrate having an insulating surface in a light emitting region.

In each of the above structures, the light emitting element emits red,green, blue, or white light.

One structure of the present invention for realizing the above structureis a method for manufacturing a light emitting device having a thin filmtransistor and a light emitting element over a substrate having aninsulating surface, comprising the steps of: forming a thin filmtransistor including a semiconductor layer having a source region, adrain region, and a channel formation region therebetween, a gateinsulating film, and a gate electrode over a first substrate having aninsulating surface; forming a highly thermostable planarizing film overan uneven shape reflected by the thin film transistor; forming anopening portion which has a tapered shape on a side face and is locatedover the source region or the drain region, and a peripheralportion-having a tapered shape by selectively removing the highlythermostable planarizing film; forming a contact hole which reaches thesource region or the drain region by selectively removing the gateinsulating film; forming an electrode which reaches the source region orthe drain region; forming an anode containing SiOx to be in contact withthe electrode; forming a bank covering an edge portion of the anode;forming a layer containing an organic compound over the anode; forming acathode over the layer containing an organic compound; and sealing thelight emitting element by attaching a second substrate to the firstsubstrate with a sealant surrounding a circumference of the lightemitting element.

In the above structure, the highly thermostable planarizing film or thebank is a SiOx film including an alkyl group formed by application. Ineach of the above structures, the anode is formed by sputtering using atarget made of indium tin oxide containing SiOx.

In each of the above structures, the light emitting device is applicableto both an active matrix type and a passive matrix type.

Each layer (the interlayer insulating film, the base insulating film,the gate insulating film, the first electrode, and the transparentprotective layer) of a light emitting device may contain silicon,thereby improving each layer of adhesiveness. Another structure of thepresent invention is a light emitting device comprising a plurality oflight emitting elements having a cathode, a layer containing an organiccompound, and an anode, wherein a highly thermostable planarizing filmcontaining silicon is formed over a substrate having an insulatingsurface, an anode containing silicon and a bank covering an edge portionof the anode are formed over the highly thermostable planarizing film, alayer containing an organic compound is formed over the anode, a cathodeis formed over the layer containing an organic compound, and aprotective film containing silicon is formed over the cathode.

In the above structure, a TFT using the highly thermostable planarizingfilm containing silicon as an interlayer insulating film is electricallyconnected to the anode.

Each layer (the interlayer insulating film, the base insulating film,the gate insulating film, the first electrode, the second electrode, andthe transparent protective layer) of a light emitting device may containone of silicon and silicon oxide, thereby improving each layer ofadhesiveness and improving reliability. Another structure of the presentinvention is a light emitting device comprising a plurality of lightemitting elements having a cathode, a layer containing an organiccompound, and an anode, wherein a highly thermostable planarizing filmcontaining one of silicon and silicon oxide is formed over a substratehaving an insulating surface, an anode containing one of silicon andsilicon oxide and a bank covering an edge portion of the anode areformed over the highly thermostable planarizing film, a layer containingan organic compound is formed over the anode, a cathode containing oneof silicon and silicon oxide is formed over the layer containing anorganic compound, and a protective film containing one of silicon andsilicon oxide is formed over the cathode.

In the above structure, a TFT using the highly thermostable planarizingfilm containing one of silicon and silicon oxide as an interlayerinsulating film is electrically connected to the anode.

Note that a light emitting element (an EL element) has a layercontaining an organic compound that can obtain luminescence (ElectroLuminescence) generated by applying an electric field, an anode, and acathode. The luminescence in the organic compound includes luminescencein returning to a ground state from a singlet excited state(fluorescence) and luminescence in returning to a ground state from atriplet excited state (phosphorescence). A light emitting devicemanufactured according to the present invention is applicable to casesof using either luminescence.

A light emitting element (an EL element) having an EL layer has astructure in which the EL layer is interposed between a pair ofelectrodes and the EL layer normally has a laminated structure.Typically, a laminated structure of “hole transport layer/light emittinglayer/electron transport layer” is given. The structure provides veryhigh luminous efficiency, and almost all the light emitting devices thatare currently under research and development adopt the structure.

Alternatively, a structure in which a hole inject layer, a holetransport layer, a light emitting layer, and an electron transportlayer, or a hole inject layer, a hole transport layer, a light emittinglayer, an electron transport layer, and an electron inject layer arelaminated in this order over an anode may be employed. The lightemitting layer may be doped with a fluorescent pigment or the like.Further, all of these layers may be formed by using a low molecularweight material or using a high molecular weight material. In addition,a layer containing an inorganic material may be used. Note that alllayers provided between a cathode and an anode are generically referredto as an EL layer in this specification. Therefore, all of the holeinject layer, the hole transport layer, the light emitting layer, theelectron transport layer, and the electron inject layer are included inthe EL layer.

In the light emitting device according to the present invention, adriving method for screen display is not particularly limited. Forexample, a dot-sequential driving method, a line-sequential drivingmethod, a plane-sequential driving method, or the like can be used forthe driving method. Typically, the line-sequential driving method isemployed, and a time gray scale driving method or an area gray scaledriving method may appropriately be used. In addition, a video signalinputted to a source line of the light emitting device may be an analogsignal or a digital signal. A driving circuit or the like mayappropriately be designed in accordance with the video signal.

In a light emitting device in which a video signal is digital, a videosignal inputted to a pixel includes a constant voltage (CV) video signaland a constant current (CC) video signal. The constant voltage (CV)video signal includes a signal in which voltage applied to a lightemitting element is constant (CVCV) and a signal in which currentapplied to a light emitting element is constant (CVCC). In addition, theconstant current (CC) video signal includes a signal in which voltageapplied to a light emitting element is constant (CCCV) and a signal inwhich current applied to a light emitting element is constant (CCCC).

In this specification, light extraction efficiency means a rate of lightemitted to atmospheric air from a transparent substrate of an element tolight generated in the element.

The present invention is applicable to any TFT structure. For example,the present invention can be applied to a top gate TFT, a bottom gate(inversely staggered) TFT, or a staggered TFT.

An amorphous semiconductor film, a semiconductor film including acrystal structure, a compound semiconductor film-including an amorphousstructure, or the like can appropriately be used as an active layer ofthe TFT. Further, the active layer of the TFT can be made of asemi-amorphous semiconductor film (also referred to as a microcrystalsemiconductor film) which is a semiconductor having an intermediatestructure of an amorphous structure and a crystal structure (includingsingle crystal and polycrystal) and a third state which is stable interms of free energy, and which includes a crystalline region having ashort distance order and lattice distortion. The semi-amorphoussemiconductor film includes a crystal grain of from 0.5 nm to 20 mm inat least a certain region thereof, and the Raman spectrum shifts to thelower side of wave number of 520 cm⁻¹. In addition, a diffraction peakof (111) and (220) derived from a Si crystal lattice is observed in thesemi-amorphous semiconductor film by X-ray diffraction. Thesemi-amorphous semiconductor film contains hydrogen or halogen of atleast 1 atom % as a neutralizer of a dangling bond. The semi-amorphoussemiconductor film is manufactured by performing glow dischargingdecomposition (plasma CVD) on a silicide gas. As the silicide gas, SiH₄,additionally, Si₂H₆, SiH₂Cl₂, SiHCl₃, SiCl₄, SiF₄, or the like can beused. The silicide gas may be diluted with H₂, or H₂ and one or more ofrare gas elements: He, Ar, Kr, and Ne. Dilution ratio is within therange of from 2 times to 1000 times. Pressure is roughly within therange of from 0.1 Pa to 133 Pa; power frequency, from 1 MHz to 120 MHz,preferably from 13 MHz to 60 MH; and substrate heating temperature, atmost 300° C., preferably from 100° C. to 250° C. An atmosphericconstitution impurity such as oxygen, nitrogen, or carbon as an impurityelement within a film is preferably at most 1×10²⁰ cm⁻¹, in particular,oxygen concentration is at most 5×10¹⁹/cm³, preferably, at most1×10¹⁹/cm³. Note that field-effect mobility μ of a TFT using asemi-amorphous semiconductor film as an active layer is from 1 cm²/Vsecto 10 cm²/Vsec.

In a light emitting element according to the present invention, powerconsumption can be-reduced by improving luminous efficiency, and ahalf-life-time of luminance can be lengthened. In addition, generationof heat in a panel can be suppressed, and stability of an element andreliability of a light emitting device can be improved.

These and other objects, features and advantages of the presentinvention will become more apparent upon reading of the followingdetailed description along with the accompanied drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are a cross-sectional view and a top view of the presentinvention.

FIG. 2 shows luminance-current characteristics.

FIG. 3 shows a result of an aging test.

FIGS. 4A to 4D are cross-sectional views of a light emitting element.

FIGS. 5A to 5C show an application apparatus and an edge remover.

FIG. 6 is a graph showing efficiency.

FIG. 7 is a graph showing transmittance.

FIG. 8 is a graph showing a refractive index.

FIG. 9 is a cross-sectional view of a light emitting device. (Embodiment5)

FIGS. 10A and 10B are cross-sectional views of a light emitting device.(Embodiment 6)

FIGS. 11A to 11G each show an example of electronic devices. (Embodiment7)

FIGS. 12A and 12B are graphs showing relation-between a paneltemperature and luminance and relation between a panel temperature and acathode current.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment mode of the present invention is described hereinafter.

First, a base insulating film 11 is formed over a substrate 10. In thecase of extracting light, considering a substrate 10 side as a displaysurface, a light transmitting glass substrate or quartz substrate may beused as the substrate 10. In addition, a heat-resistant lighttransmitting plastic substrate which can withstand a processingtemperature may be used. In the case of extracting light, consideringthe other side of the substrate 10 side as a display surface, a siliconsubstrate, a metal substrate, or a stainless steel substrate providedwith an insulating film over its surface as well as the above-describedsubstrate may be used. Here, a glass substrate is used as the substrate10. Note that a refractive index of the glass substrate is approximately1.55.

A base film made of an insulating film such as a silicon oxide film, asilicon nitride film, or a silicon oxynitride film is formed as the baseinsulating film 1. Although the base film has a two-layer structurehere, it may be a single layer film of the above insulating film, or mayhave a laminated structure of two or more layers. Note that the baseinsulating film need not be formed particularly.

Next, a semiconductor layer is formed over the base insulating film. Thesemiconductor layer can be formed by forming a semiconductor film havingan amorphous structure by a known method (sputtering, LPCVD, plasma CVD,or the like), and thereafter, patterning a crystalline semiconductorfilm obtained by known crystallization treatment (laser crystallization,thermal crystallization, thermal crystallization using a catalyst suchas nickel, or the like) with the use of a first photomask to have adesired shape. The semiconductor layer is formed to have a thickness offrom 25 nm to 80 nm (preferably, from 30 nm to 70 nm). There is noparticular limitation on a material of the crystalline semiconductorfilm; however, the crystalline semiconductor film may preferably be madeof silicon, a silicon-germanium (SiGe) alloy, or the like.

In addition, a continuous wave laser may be used for crystallizationtreatment of the semiconductor film having an amorphous structure. Inthe case of crystallizing the amorphous semiconductor film, it ispreferable to apply a second harmonic to a fourth harmonic of afundamental wave by using a solid laser which can continuously oscillatein order to obtain a crystal with a large grain size. Typically, asecond harmonic (532 nm) or a third harmonic (355 nm) of an Nd: YVO₄laser (a fundamental wave, 1064 nm) may be applied. In the case of usingthe continuous wave laser, laser light emitted from a continuous waveYVO₄ laser having output of 10 W is converted to a harmonic by anonlinear optical element. There is also a method for emitting aharmonic by putting a YVO₄ crystal and the nonlinear optical element ina resonator. Then, the harmonic is preferably shaped into rectangular orelliptical laser light on an irradiated surface by an optical system andan object to be treated is irradiated therewith. At this time, theenergy density of approximately from 0.01 MW/cm² to 100 MW/cm²(preferably, from 0.1 MW/cm² to 10 MW/cm²) is required. Thesemiconductor film may be irradiated by being moved relatively to thelaser light at the speed of approximately from 10 cm/s to 2000 cm/s.

Subsequently, an insulating film 12 covering the semiconductor layer isformed after the resist mask is removed. The insulating film 12 isformed by plasma CVD or sputtering to have a thickness of from ˜1 nm to200 nm. Preferably, surface nitriding treatment using plasma by amicrowave is performed after the insulating film 12 is formed to be asingle layer or to have a laminated structure of an insulating filmcontaining silicon so that a thickness thereof is made thin, from 10 nmto 50 nm.

When plasma CVD is used for forming such a thin insulating film, it isnecessary to obtain a thin film thickness with good controllability bylatening a formation rate. For example, film formation speed of thesilicon oxide film can be set at 6 nm/min when RF power is set at 100 W,10 kHz; pressure, 0.3 Torr; an N₂O gas flow, 400 sccm; and a SiH₄ gasflow, 1 sccm. The nitriding treatment with the use of plasma by amicrowave is performed with the use of a microwave source (2.45 GHz) anda nitrogen gas which is a reactive gas.

Note that the nitrogen concentration decreases as departing from thesurface of the insulating film 12. Consequently, the surface of thesilicon oxide film can be nitrided at high concentration. In addition,deterioration of device properties can be prevented by reducing nitrogenat the interface between the silicon oxide film and an active layer.Note that the insulating film 12 having the surface on which nitridingtreatment is performed serves as a gate insulating film of a TFT.

Next, a conductive film is formed over the insulating film 12 to have athickness of from 100 nm to 600 nm. Here, a conductive film having alaminated structure of a TaN film and a W film is formed by usingsputtering. The laminate of the TaN film and the W film is given here asthe conductive film, but the conductive film is not limited thereto. Asfor the conductive film, a single layer of one element of Ta, W, Ti, Mo,Al, and Cu, an alloy material or a compound material containing theelement as its main component, or a laminate thereof can be used. Asemiconductor film typified by a polycrystalline silicon film doped withan impurity element such as phosphorous may also be used.

Subsequently, a resist mask is formed by using a second photomask, andetching is performed by dry etching or wet etching. In this etchingstep, the conductive film is etched to obtain conductive layers 14 a, 14b, 15 a, and 15 b. Note that the conductive layers 14 a and 14 b serveas gate electrodes of the TFT and the conductive layers 15 a and 15 bserve as terminal electrodes.

Next, a resist mask is newly formed by using a third photomask afterremoving the resist mask. A first doping step for doping an impurityelement which imparts n-type conductivity to a semiconductor (typically,phosphorus or As) at low concentration is performed to form an n-channelTFT not shown herein. The resist mask covers a region to be a p-channelTFT and a vicinity of the conductive layer. A low concentration impurityregion is formed by performing through-dope through the insulating filmby the first doping step. A plurality of TFTs is used to drive one lightemitting element. However, the above-mentioned doping step is notnecessary when the light emitting element is driven by only a p-channelTFT.

Then, a resist mask is newly formed by using a fourth photomask afterremoving the resist mask. A second doping step is performed to dope animpurity element which imparts p-type conductivity to a semiconductor(typically, boron) at high concentration. P-type high concentrationimpurity regions 17 and 18 are formed by performing through-dope throughthe insulating film 12 by the second doping step.

Then, a resist mask is newly formed by using a fifth photomask. A thirddoping step for doping an impurity element which imparts n-typeconductivity to a semiconductor (typically, phosphorus or As) at highconcentration is performed to form an n-channel TFT not shown herein.The third doping step is performed under the condition that the amountof doze is set at from 1×10¹³/cm² to 5×10¹⁵/cm²; and the accelerationvoltage, from 60 keV to 100 keV. The resist mask covers the region to bethe p-channel TFT and a vicinity of the conductive layer. Through-dopeis performed through the insulating film 12 by the third doping step toform an n-type high concentration impurity region.

Afterwards, activation and hydrogenation of the impurity element addedto the semiconductor layer are performed after removing the resist maskand forming an insulating film containing hydrogen 13. The insulatingfilm containing hydrogen 13 is made of a silicon nitride oxide film(SiNO film) obtained by PCVD. In addition, gettering for reducing nickelin a channel formation region 19 can also be performed at the same timeas activation, when the semiconductor film is crystallized by using ametal element which promotes crystallization, typically, nickel. Notethat the insulating film containing hydrogen 13 is a first interlayerinsulating film and contains silicon oxide.

Then, a highly thermostable planarizing film 16 to be a secondinterlayer insulating film is formed. As the highly thermostableplanarizing film 16, an insulating film in which a skeletal structure isformed by the bond of silicon (Si) and oxygen (O) obtained byapplication is used. Thus, the second interlayer insulating filmcontains silicon oxide.

Here, a procedure for forming the highly thermostable planarizing film16 is described in detail with reference to FIGS. 5A to 5C.

First, a substrate to be treated is washed with purified water.Megasonic washing may be performed. Next, after performing dehydrobakingfor 110 seconds at a temperature of 140° C., a temperature of thesubstrate is regulated by cooling for 120 seconds with a water-cooledplate. Next, the substrate is transferred to and placed in a spinningapplication apparatus shown in FIG. 5A.

FIG. 5A shows a cross-sectional schematic diagram of the spinningapplication apparatus. In FIG. 5A, reference numeral 1001 denotes anozzle; 1002, a substrate; 1003, an application cup; and 1004, anapplication material solution. The spinning application apparatus has amechanism that the application material solution is dropped from thenozzle 1001, the substrate 1002 is horizontally placed in theapplication cup 1003, and the entire application cup rotates. Thespinning application apparatus has also a mechanism that the pressure ofatmosphere in the application cup 1003 can be controlled.

Next, pre-wet application is performed to improve wettability by usingan organic solvent such as thinner (a volatile mixture solvent mixedwith aromatic hydrocarbon (toluene or the like), alcohols, esteracetate, or the like). Thinner is spread thoroughly over the substratewith centrifugal force by spinning the substrate (rotation number, 100rpm) as 70 ml of the thinner is dropped, and then, the thinner is spunoff by spinning the substrate at high speed (rotation number, 450 rpm).

Subsequently, the application material solution is thoroughly spreadwith centrifugal force by gradually spinning (rotation number, from 0rpm to 1000 rpm) the substrate as the application material solution usedfor a liquid material in which a siloxane polymer is dissolved in asolvent (propylene glycolmonomethyl ether (molecular formula:CH₃OCH₂CH(OH)CH₃)) is dropped from the nozzle 1001. The siloxane polymercan be classified in terms of a siloxane structure into silica-glass, analkyl siloxane polymer, an alkyl silsesquioxane polymer, silsesquioxanepolymer hydride, and the like, for example. PSB-K1 and PSB-K31 which areapplication insulating film materials manufactured by Toray Industries,Inc., or ZRS-5PH which is an application insulating film materialmanufactured by Catalysts & Chemicals Industries Co., Ltd. can be givenas an example of the siloxane polymer. Then, the substrate is graduallyspun (rotation number, from 0 rpm to 1400 rpm) after holding thesubstrate for 30 seconds to perform leveling on the application film.

Inside of the application cup 1003 is exhausted to be under reducedpressure, and then, drying under reduced pressure is performed within 1minute.

Edge removing treatment is performed by an edge remover provided for thespinning application apparatus shown in the FIG. 5A. FIG. 5B shows anedge remover 1006 provided with a driving means which moves in parallelalong the periphery of the substrate 1002. In the edge remover 1006, athinner discharging nozzle 1007 as shown in FIG. 5C is provided side byside to sandwich one side of the substrate, and a peripheral portion ofthe application film 1008 is dissolved by the thinner. Thereafter, theapplication film in the peripheral portion of a substrate end face isremoved by exhausting liquid and gas in an arrow direction shown in thefigure.

Then, pre-baking is performed by baking for 170 seconds at a temperatureof 110° C.

Subsequently, the substrate is carried out of the spinning applicationapparatus and is cooled. Thereafter, baking is further performed for onehour at a temperature of 270° C. Thus, the highly thermostableplanarizing film 16 having a thickness of 0.8 μm is formed. Whensmoothness of the obtained highly thermostable planarizing film 16 ismeasured by an AFM (atomic force microscope), a P-V value (Peak toValley, a difference between a maximum value and a minimum value ofheight) is approximately 5 nm and a value of Ra (average surfaceroughness) is approximately 0.3 nm within a region of 10 μm×10 μm.

Transmittance can be changed by changing a baking temperature of thehighly thermostable planarizing film 16. FIG. 7 shows transmittance ofthe highly thermostable planarizing film (SiOx film including an alkylgroup) having a thickness of 0.8 μm under two baking temperatureconditions (270° C. and 410° C.), and FIG. 8 shows a refractive indexthereof. Transmittance improves in the case of setting a bakingtemperature at 410° C., in comparison with the case of at 270° C.Further, a refractive index decreases in the case of setting a bakingtemperature at 410° C.

In addition, the highly thermostable planarizing film 16 may be formedby ink-jet. A material solution can be saved in the case of employingink-jet.

Subsequently, a third interlayer insulating film 21 is formed. Beforethe third interlayer insulating film is formed, heating is performed forone hour at a temperature of 250° C. for dehydration. A silicon nitrideoxide film (SiNO film: 100 nm in thickness) obtained by PCVD is used asthe third interlayer insulating film 21. This interlayer insulating film21 is provided as an etching stopper film for protecting the highlythermostable planarizing film 16 that is the second interlayerinsulating film when 23R and 23G are patterned in the following step.Note that the third interlayer insulating film 21 also contains siliconoxide.

FIG. 12A shows relation between a panel temperature and luminance. FIG.12B shows relation between a panel temperature and a cathode current ofa light emitting panel driven by CVCC. In FIGS. 12A and 12B, acomparative example is an active matrix light emitting panel using ITOas an anode and using a laminate of an acrylic resin and a siliconnitride film by sputtering as an interlayer insulating film. A sample Ais an active matrix light emitting panel using ITSO as an anode andusing a laminate of an acrylic resin and a silicon nitride film bysputtering as an interlayer insulating film. A sample B is an activematrix light emitting panel using ITSO as an anode and using a laminateof an application film with the use of a siloxane polymer (PSB-K31) anda SiNO film by PCVD as an interlayer insulating film.

FIG. 12A shows that rise in a panel temperature according to rise inluminance is suppressed most in the sample B. FIG. 12B shows that risein a panel temperature according to rise in a cathode current is alsosuppressed most in the sample B. These results show that Joule heatgenerated in a panel is suppressed in the sample B which is an exampleof structures of the present invention. Suppression of heat generated ina panel leads to improvement in reliability of a light emitting device.

Subsequently, the interlayer insulating film 21 in the peripheralportion is removed at the same time as forming a contact hole in theinterlayer insulating film 21 with the use of a sixth mask. Etchingtreatment is performed on the interlayer insulating film 21, using CHF₃and Ar as an etching gas.

Thereafter, etching is performed using the sixth mask without change asa mask, thereby removing the highly thermostable planarizing film in theperipheral portion at the same time as forming a contact hole in thehighly thermostable planarizing film 16. Here, etching (wet etching ordry etching) is performed under such a condition that selection ratiowith the insulating film 13 can be obtained. Although there is nolimitation on an etching gas to be used, it is suitable to use CF₄, O₂,He, or Ar here. Dry etching is performed with the flow of CF₄ of 380sccm; the flow of O₂, 290 sccm; the flow of He, 500 sccm; the flow ofAr, 500 sccm; RF power, 300.0 W; and pressure, 25 Pa. Note that etchingtime may be increased by approximately from 10% to 20% in order toperform etching without leaving a residue over a surface of theinsulating film 13. Etching may be conducted once or a plurality oftimes to obtain a tapered shape. Here, the tapered shape is obtained byfurther performing a second dry etching using CF₄, O₂, and He with theflow of CF₄ of 550 sccm; the flow of O₂, 450 sccm; the flow of He, 350sccm; RF power, 3000 W; and pressure, 25 Pa. It is desirable to set ataper angle θ of an edge portion of the highly thermostable planarizingfilm at more than 30° and less than 75°.

In addition, doping treatment of an inert element may be performed on anedge portion of the highly thermostable planarizing film to form ahighly densified portion in the tapered portion of the highlythermostable planarizing film. The doping treatment may be performed byion doping or ion implantation. Typically, argon (Ar) is used as theinert element. Distortion is given by adding an inert element having acomparatively large atomic radius, and a surface (including a side wall)is modified or highly densified, thereby preventing entry of moisture oroxygen. The inert element contained in the highly densified portion isset at within the concentration range of from 1×10¹⁹/cm³ to 5×10²¹/cm³,typically, from 2×10¹⁹/cm³ to 2×10²¹/cm³. Note that the edge portion ofthe highly thermostable planarizing film is formed to have a taperedshape, so that the side wall of the highly thermostable planarizing filmis easy to be doped.

Subsequently, etching is performed using the sixth mask without changeas a mask to selectively remove exposed insulating films 12 and 13. Theetching treatment is performed on the insulating films 12 and 13 byusing CHF₃ and Ar as an etching gas. Note that etching time may beincreased by approximately from 10% to 20% in order to perform etchingwithout leaving a residue over the semiconductor layer.

After removing the sixth mask and forming a conductive film(TiN/Al/Tin), etching (dry etching with a mixed gas of BCl₃ and Cl₂) isperformed using a seventh mask to form a wiring 22. Note that TiN is oneof materials having preferable adhesiveness with the highly thermostableplanarizing film. In addition, it is preferable to set N content of TiNat less than 44% to be in contact with a source region or a drain regionof a TFT.

Subsequently, first electrodes 23R and 23G, in other words, an anode (ora cathode) of an organic light emitting element is formed with the useof an eighth mask. A film containing as its main component one elementof Ti, TiN, TiSi_(X)N_(Y), Ni, W, WSi_(X), WN_(X), WSi_(X)N_(Y), NbN,Cr, Pt, Zn, Sn, In, and Mo, an alloy material or a compound materialcontaining the element as its main component, or a laminate thereof maybe used as a material of the first electrodes 23R and 23G within therange of from 100 nm to 800 nm in thickness in total.

In the case of extracting light, considering the substrate 10 side as adisplay surface, ITSO (indium tin oxide containing silicon oxide formedby using a target made of ITO containing silicon oxide of from 2% to 10%by weight) is used as a material of the first electrode. In addition toITSO, a transparent conductive film such as a light transmitting oxideconductive film which contains silicon oxide and in which indium oxideis mixed with zinc oxide (ZnO) of from 2% to 20% may also be used.Moreover, a transparent conductive film of ATO (antimony tin oxide)containing silicon oxide may be used.

Subsequently, an insulator 29 (referred to as a bank, a partition wall,a barrier, or the like) is formed using a ninth mask to cover edgeportions of the first electrodes 23R and 23G. An SOG film (for example,a SiOx film including an alkyl group) obtained by application may beused for the insulator 29 within the range of from 0.8 μm to 1 μm inthickness. Either dry etching or wet etching can be performed as theetching; however, the insulator 29 is formed by dry etching using amixed gas of CHF₃, O₂, and He here. In the dry etching, an etching rateof the SiOx film including an alkyl group is from 500 nm/min to 600nm/min, and on the other hand, an etching rate of an ITSO film is equalto or less than 10 nm/min; thus, sufficient selection ratio is obtained.A TiN film having good adhesiveness is a top surface, since the wiring22 is covered with the insulator 29 made of the SiOx film including analkyl group.

Next, layers containing an organic compound 24H, 24R, 24E, and 24G areformed by evaporation or application. It is preferable to perform vacuumheating and deaeration before forming the layers containing an organiccompound 24H, 24R, 24E, and 24G in order to improve reliability. Forexample, it is preferable to perform heat treatment at a temperature offrom 200° C. to 300° C. under a reduced pressure atmosphere or an inertatmosphere in order to remove a gas included in the substrate, beforeevaporating an organic compound material. Here, the interlayerinsulating film and the bank are made of a highly thermostable SiOxfilm; therefore, heat treatment at high temperature does not cause aproblem.

In the case of forming the layer containing an organic compound byapplication using spin coating, an application layer is preferably bakedby vacuum heating. For example, an aqueous solution of poly(ethylenedioxythiophene)/poly(styrene sulfonic acid) (PEDOT/PSS) to serve as ahole inject layer 24H may be applied to an entire surface and be baked.In addition, the hole inject layer may be formed by evaporation.

Subsequently, evaporation is employed to form the layers containing anorganic compound 24R, 24G; and 24E, and the evaporation is performed ina film formation chamber which is vacuum evacuated to at most 5×10⁻³Torr(0.665 Pa), preferably from 10⁻⁴ Torr to 10⁻⁶ Torr. The organic compoundis preliminarily vaporized by resistance heating in evaporating. Thevaporized organic compound is scattered in the direction of thesubstrate by opening a shutter at the time of evaporation. The vaporizedorganic compound is scattered upwardly and is evaporated over thesubstrate through an opening provided for a metal mask.

A mask is aligned for every color of light emission (R, G, and B) toperform full color display.

For example, Alq₃ added with DCM is deposited to be 40 nm as the lightemitting layer 24R. In addition, Alq₃ added with DMQD is formed to be 40nm as the light emitting layer 24G. Although not shown here, PPD(4,4′-bis(N-(9-phenanthryl)-N-phenylamino)biphenyl) added with CBP(4,4′-bis(N-carbazolyl)-biphenyl) is formed to be 30 nm as a blue lightemitting layer, and SAlq(bis(2-metyl-8-quinolinolate)(triphenylsilanolate)aluminum) is formed tobe 10 nm as a blocking layer.

Subsequently, Alq₃ is formed to be 40 μm as an electron transport layer24E.

Thereafter, a second electrode 25, that is, a cathode (or an anode) ofthe organic light emitting element is formed. An alloy film such asMgAg, MgIn, AlLi, CaF₂, or CaN, or a film in which an element belongingto Group 1 or 2 in the periodic table and aluminum are formed byco-evaporation may be used as a material of the second electrode 25. Inthe case of making the second electrode 25 light transmitting, analuminum film or an aluminum film that contains a minute amount of Lihaving a thickness of from 1 nm to 10 nm is used, and a transparentconductive film may be formed thereover.

Further, a light transmitting layer (film thickness of from 1 nm to 5nm) made of CaF₂, MgF₂, or BaF₂ may be formed as a cathode buffer layerbefore forming the second electrode 25.

In addition, a protective layer for protecting the second electrode 25may be formed. For example, a protective film made of a silicon nitridefilm can be formed by using a diskform target made of silicon and bymaking the atmosphere inside the film formation chamber a nitrideatmosphere or an atmosphere including nitride and argon. Further, asilicon nitride oxide film may be formed as the protective film.Further, a thin film containing carbon as its main component (a DLCfilm, a CN film, or an amorphous carbon film) may be formed as theprotective film, and a CVD chamber may be provided separately. Adiamond-like carbon film (also referred to as a DLC film) can be formedby a method such as plasma CVD (typically, RF plasma CVD, microwave CVD,electron cyclotron resonance (ECR) CVD, or hot filament CVD), combustionflame, sputtering, ion beam evaporation, or laser evaporation. Ahydrogen gas and a hydrocarbon gas (for example, CH₄, C₂H₂, C₆H₆, or thelike) are used as a reaction gas used for film formation and aresubjected to ionization with glow discharging. Ions are accelerated forcollision against a cathode to which negative self-bias is applied toform a film. In addition, the CN film may be formed by using a C₂H₄ gasand an N₂ gas as a reaction gas. Note that the DLC film and the CN filmare insulating films transparent or translucent to visible light. Theterm “transparent to visible light” used herein means that transmittanceof visible light is in the range of from 80% to 1100% while the term“translucent to visible light” used herein means that transmittance ofvisible light is in the range of from 50% to 80%. Note that theprotective film need not be provided when it is not required.

Next, the light emitting element is sealed by attaching a sealingsubstrate 33 with a sealant 28. The sealing substrate is attached sothat the sealant 28 covers an edge portion (tapered portion) of thehighly thermostable planarizing film 16. Note that a region surroundedby the sealant 28 is filled with a transparent filler 27. There is noparticular limitation on the filler 27 as long as the filler is a lighttransmitting material. Typically, an ultraviolet curable or heat curableepoxy resin may be used. Here, a highly thermostable UV epoxy resin(product name: 2500 Clear, manufactured by Electrolite Cooperation) maybe used, which has a refractive index of 1.50, a viscosity of 500 cps, aShore D hardness of 90, a tensile strength of 3000 psi, a Tg point of150° C., volume resistivity of 1×10¹⁵ Ω·cm, and a withstand voltage of450 V/mil. In addition, total transmittance can be improved by fillinginterspace between a pair of the substrates with the filler 27.

Lastly, an FPC 32 is attached to the terminal electrodes 15 a and 15 bwith an anisotropic conductive film 31 by a known method. The terminalelectrodes 15 a and 15 b are formed simultaneously with a gate wiring.(FIG. 1A)

FIG. 1B is a top view. An edge portion 34 of the highly thermostableplanarizing film is covered with the sealant 28 as shown in FIG. 1B. Across-sectional view taken along a chained line A-B in FIG. 1Bcorresponds to FIG. 1A.

In the thus manufactured active matrix light emitting device, the highlythermostable planarizing film 16, typically, a material in which askeletal structure is formed by the bond of silicon (Si) and oxygen (O)is used for an interlayer insulating film of the TFT. The bank is alsomade of the same material and the first electrode contains siliconoxide. The active matrix light emitting device is made of a materialincluding silicon oxide which is comparatively stable. Accordingly,reliability of the light emitting device is increased.

When the first electrode is made of a transparent material and thesecond electrode is made of a metal material, the light emitting devicehas a structure for extracting light through the substrate 10, that is,a bottom emission type. When the first electrode is made of a metalmaterial and the second electrode is made of a transparent material, thelight emitting device has a structure for extracting light through thesealing substrate 33, that is, a top emission type. When the firstelectrode and the second electrode are made of a transparent material,the light emitting device has a structure for extracting light throughboth the substrate 10 and the sealing substrate 33. In the presentinvention, any one of the structures may appropriately be employed.

Silicon oxide (approximately, 1.46) is contained in layers through whichlight emitted from a light emitting layer passes, that is, all of thefirst electrode, the first interlayer insulating film 13, the secondinterlayer insulating film 16, the third interlayer insulating film 21,the gate insulating film 12, and the base insulating film 11. Therefore,difference in each refractive index decreases and light extractionefficiency increases in the case of extracting light through thesubstrate 10. In other words, stray light among material layers havingdifferent refractive indexes can be reduced.

FIG. 2 shows current-luminance characteristics of the light emittingdevice. As shown in FIG. 2, luminance of a sample 1 and a sample 2 isimproved by up to half, compared with a comparative example. In thesample 1 and the sample 2, the highly thermostable planarizing filmobtained by application with the use of a siloxane polymer is used asthe second interlayer insulating film, and ITSO is used as the firstelectrode. However, acrylic is used for the bank of the sample 1 and thesample 2. In the comparative example, ITO is used as the firstelectrode, acrylic obtained by application is used as the secondinterlayer insulating film, and acrylic is used as the bank.

FIG. 3 shows each result of a room temperature aging test of the sample1, the sample 2, and the comparative example. The present invention iseffective in long-term reliability as shown in FIG. 3.

Further, the present invention can prevent increase in panel temperatureaccompanied with increase in luminance or increase in a cathode current,as shown in FIGS. 12A and 12B.

The present invention having the above structures is described in moredetail in the following embodiments.

[Embodiment 1]

An example of a bottom emission light emitting device is described inthis embodiment with reference to FIG. 4C.

First, a TFT which is connected to a light emitting element ismanufactured over a light transmitting substrate (glass substrate: arefractive index of approximately 1.55). Since the light emitting deviceis a bottom emission type, a highly light transmitting material is usedfor an interlayer insulating film, a gate insulating film, and a baseinsulating film. Here, a SiNO film formed by PCVD is used as first andthird interlayer insulating films. A SiOx film formed by application isused as a second interlayer insulating film.

Subsequently, a first electrode 323 which is electrically connected tothe TFT is formed. An ITSO film which is a transparent conductive filmcontaining SiOx (film thickness: 100 nm) is used for the first electrode323. The ITSO film is formed by sputtering using a target in whichindium tin oxide is mixed with silicon oxide (SiO₂) of from 1% to 10%with Ar gas flow rate of 120 sccm, O₂ gas flow rate of 5 sccm, pressureof 0.25 Pa, and electric power of 3.2 kW. Then, heat treatment isperformed for one hour at a temperature of 200° C., after forming theITSO film.

Subsequently, a bank 329 is formed to cover a peripheral edge portion ofthe first electrode 323. The bank 329 can be made of an inorganicmaterial (silicon oxide, silicon nitride, silicon oxynitride, or thelike), a photosensitive or non-photosensitive organic material(polyimide, acrylic, polyamide, polyimideamide, a resist, orbenzocyclobutene), an SOG film obtained by application (for example, aSiOx film including an alkyl group), a laminate of these materials, orthe like.

In this embodiment, the bank 329 is patterned by wet etching to have acurved surface with a radius of curvature only in its top edge portion.For instance, it is preferable to use a positive photosensitive acrylicas the bank 329 and to make only a top edge portion of the bank have acurved surface with a radius of curvature. Both a negativephotosensitive material that is insoluble in an etchant by irraditationof light to which the material is photosensitive and a positivephotosensitive material that is soluble in an etchant by irradiation oflight can be used for the insulator.

Subsequently, a layer containing an organic compound 324 is formed byevaporation or application. A light emitting element which emits greenlight is formed in this embodiment. CuPc (20 nm) and NPD (40 nm) arelaminated by evaporation, and Alq₃ doped with DMQd (37.5 nm), Alq₃ (37.5nm), and CaF₂ (1 nm) are sequentially laminated by co-evaporation.

An alloy film such as MgAg, MgIn, AlLi, CaF₂, or CaN, or a film in whichan element belonging to Group 1 or 2 in the periodic table and aluminumare formed by co-evaporation may be used as the second electrode 325. Inthis embodiment, Al is evaporated to have a thickness of 200 nm. Inaddition, a protective film may be laminated if necessary.

Subsequently, the light emitting element is sealed by attaching asealing substrate 333 with a sealant (not shown). A space 327 betweenthe sealing substrate and the second electrode is filled with an inertgas or a filler made of a transparent resin.

A bottom emission light emitting device is completed according to theabove steps. In this embodiment, a refractive index or film thickness ofeach layer (the interlayer insulating film, the base insulating film,the gate insulating film, or the first electrode) is determined withinan adjustable range. Accordingly, light reflection at an interface ofthe layer is reduced and light extraction efficiency is improved.

[Embodiment 2]

An example of a top emission light emitting device is described in thisembodiment with reference to FIG. 4A.

First, a TFT which is connected to a light emitting element ismanufactured over a substrate having an insulating surface. Since thelight emitting device is a top emission type, a light transmittingmaterial need not necessarily be used for an interlayer insulating film,a gate insulating film, and a base insulating film. In this embodiment,a SiNO film formed by PCVD is used for first and third interlayerinsulating film as a highly stable material film. A SiOx film formed byapplication is used for a second interlayer insulating film as a highlystable material film.

Further, a fourth interlayer insulating film 211 is provided. The SiOxfilm formed by application is used also for the fourth interlayerinsulating film 211.

Subsequently, the fourth interlayer-insulating film 211 is selectivelyetched to form a contact hole reaching an electrode of the TFT.Thereafter, a reflective metal film (Al—Si film (film thickness: 30nm)), a material film having a large work function (TiN film (filmthickness: 10 nm)), and a transparent conductive film (ITSO film (filmthickness: from 10 nm to 100 nm)) are sequentially formed. Then,patterning is performed to form a reflecting electrode 212 and a firstelectrode 213 which are electrically connected to the TFT.

Subsequently, a bank 219 is formed to cover an edge portion of the firstelectrode 213. The bank 219 can be made of an inorganic material(silicon oxide, silicon nitride, silicon oxynitride, or the like), aphotosensitive or non-photosensitive organic material (polyimide,acrylic, polyamide, polyimideamide, a resist, or benzocyclobutene), anSOG film obtained by application (for example, a SiOx film including analkyl group), or a laminate of these materials.

Next, a layer containing an organic compound 214 is formed byevaporation or application.

An aluminum film or an aluminum film that contains a minute amount ofLi, having a thickness of from 1 nm to 10 nm is used for a secondelectrode 215 in order to make the light emitting device a top emissiontype. In addition, a transparent conductive film comprising one of ITSOand ITO may be laminated if necessary.

Subsequently, a transparent protective layer 216 is formed byevaporation, sputtering or plasma CVD. The transparent protective layer216 is made of a silicon nitride oxide film (SiNO film) or a siliconnitride film (SiN film). The transparent protective layer 216 protectsthe second electrode 215.

Then, the light emitting element is sealed by attaching a sealingsubstrate 203 with a sealant. Note that a region surrounded by thesealant is filled with a transparent filler 217. There is no particularlimitation on the filler 217 as long as the filler is a lighttransmitting material. Typically, an ultraviolet curable or heat curableepoxy resin may be used. In addition, total transmittance can beimproved by filling interspace between a pair of substrates with thefiller 217.

According to the above steps, the top emission light emitting device iscompleted. In this embodiment, each layer (the interlayer insulatingfilm, the base insulating film, the gate insulating film, and the firstelectrode) contains SiOx, thereby improving reliability.

[Embodiment 3]

A top emission light emitting device which is different from that ofEmbodiment 2 is described in this embodiment with reference to FIG. 4B.

First, a TFT which is connected to a light emitting element ismanufactured over a substrate having an insulating surface. Since thelight emitting device is a top emission type, a light transmittingmaterial is not necessarily used for an interlayer insulating film, agate insulating film, or a base insulating film. In this embodiment, aSiNO film obtained by PCVD is used for first and third interlayerinsulating film as a highly stable material film. Further, a SiOx filmobtained by application is used for a second interlayer insulating filmas a highly stable material film. The interlayer insulating film and thegate insulating film are selectively etched to form a contact holereaching an active layer of the TFT. After a conductive film(TiN/Al—Si/TiN) is formed, it is etched (dry etching with a mixed gas ofBCl₃ and Cl₂) by using a mask to form a source electrode and a drainelectrode of the TFT.

Subsequently, a first electrode 223 which is electrically connected tothe drain electrode (or the source electrode) of the TFT is formed. Asfor a material of the first electrode 223, a material having a largework function, for example, a film containing as its main component oneelement of TiN, TiSi_(X)N_(Y), Ni, W, WSi_(X), WN_(X), WSi_(X)N_(Y),NbN, Cr, Pt, Zn, Sn, In, or Mo, an alloy material or a compound materialcontaining the element as its main component, or a laminated filmthereof may be used within the range of from 100 nm to 800 nm in thickin total.

Subsequently, a bank 229 is formed to cover a peripheral edge portion ofthe first electrode 223. An SOG film obtained by application (forexample, a SiOx film including an alkyl group) is used for the bank 229.The bank 229 is formed to have a desired shape by dry etching.

Next, a layer containing an organic compound 224 is formed byevaporation or application.

An aluminum film or an aluminum film that contains a minute amount ofLi, having a thickness of from 1 nm to 10 nm is used for a secondelectrode 225 in order to make the light emitting device a top emissiontype. In addition, a transparent conductive film (for example, an ITSOfilm) may be laminated if necessary.

Subsequently, a transparent protective layer 226 is formed byevaporation or sputtering. The transparent protective layer 226 protectsthe second electrode 225.

Next, the light emitting element is sealed by attaching a sealingsubstrate 233 with a sealant. Note that a region surrounded by thesealant is filled with a transparent filler 227. There is no particularlimitation on the filler 227 as long as the filler is a lighttransmitting material. Typically, an ultraviolet curable or heat curableepoxy resin may be used. In addition, total transmittance can beimproved by filling interspace between a pair of substrates with thefiller 227.

According to the above steps, the top emission light emitting device iscompleted. In this embodiment, each layer (the interlayer insulatingfilm, the base insulating film, the gate insulating film, and the bank)contains SiOx, thereby-improving reliability.

[Embodiment 4]

An example of a light emitting device in which light can be extractedfrom both substrates is described with reference to FIG. 4D.

First, a TFT which is connected to a light emitting element ismanufactured over a light transmitting substrate (glass substrate: arefractive index of approximately 1.55). Since the light emitting deviceof this embodiment performs display by passing light through atransparent substrate, a highly light transmitting material is used foran interlayer insulating film, a gate insulating film, and a baseinsulating film. Here, a SiNO film formed by PCVD is used as first andthird interlayer insulating films. A SiOx film formed by application isused as a second interlayer insulating film.

Subsequently, a first electrode 423 which is electrically connected tothe TFT is formed. ITSO that is a transparent conductive film containingSiOx (film thickness: 100 nm) is used for the first electrode 423.

Subsequently, a bank 429 is formed to cover a peripheral edge portion ofthe first electrode 423. The bank 429 can be made of an inorganicmaterial (silicon oxide, silicon nitride, silicon oxynitride, or thelike), a photosensitive or non-photosensitive organic material(polyimide, acrylic, polyamide, polyimideamide, a resist, orbenzocyclobutene), an SOG film obtained by application (for example, aSiOx film including an alkyl group), or a laminate of these materials.

In this embodiment, the bank 429 is patterned by wet etching to have acurved surface with a radius of curvature only in its top edge portion.

Subsequently, a layer containing an organic compound 424 is formed byevaporation or application.

An aluminum film or an aluminum film that contains a minute amount ofLi, having a thickness of from 1 nm to 10 nm is used for a secondelectrode 425 in order to extract light to a sealing substrate side. Inaddition, a transparent conductive film may be laminated if necessary.

Subsequently, a transparent protective layer 426 is formed byevaporation or sputtering. The transparent protective layer 426 protectsthe second electrode 425.

Next, the light emitting element is sealed by attaching a sealingsubstrate 433 with a sealant. A light transmitting substrate (glasssubstrate: a refractive index of approximately 1.55) is used also as thesealing substrate 433. Note that a region surrounded by the sealant isfilled with a transparent filler 427. There is no particular limitationon the filler 427 as long as the filler is a light transmittingmaterial. Typically, an ultraviolet curable or heat curable epoxy resinmay be used. In addition, total transmittance can be improved by fillinginterspace between a pair of substrates with the filler 427.

In a light-emitting device which emits light on both sides as shown inFIG. 4D, two pieces of polarizing plates are disposed to sandwich alight-emitting panel so that a direction of polarization of light is tobe perpendicular thereto. Accordingly, a display can be prevented frombeing hard to be recognized because of transparency to see a backgroundwhen watched from one side.

[Embodiment 5]

An example of selectively adding an inert element to a peripheralportion of an interlayer insulating film in order to prevent moistureentry from an external surface of the interlayer insulating film isdescribed in this embodiment.

Each semiconductor layer is formed after a base insulating film isformed over a substrate 610. Subsequently, each gate electrode and eachterminal electrode are formed after a gate insulating film covering thesemiconductor layer is formed. Subsequently, a source region and a drainregion, and an LDD region if necessary, are appropriately formed bydoping an impurity element which imparts n-type conductivity to asemiconductor (typically, phosphorus or As) to form an n-channel TFT 636and by doping an impurity element which imparts p-type conductivity to asemiconductor (typically, boron) to form a p-channel TFT 637.Subsequently, the impurity element added to the semiconductor layer isactivated and hydrogenated after forming a silicon nitride oxide film(SiNO film) which contains hydrogen and which is obtained by PCVD.

Subsequently, a highly thermostable planarizing film 616 which serves asan interlayer insulating film is formed. As the highly thermostableplanarizing film 616, an insulating film in which a skeletal structureis formed by the bond of silicon (Si) and oxygen (O) obtained byapplication is used. Then, a SiNO film is formed by PCVD. Note that thesteps up to here are almost the same as those described in theembodiment mode.

Next, the highly thermostable planarizing film in a peripheral portionis removed at the same time as forming a contact hole in the SiNO filmand the highly thermostable planarizing film by using a mask. Etchingmay be performed once or a plurality of times to obtain a tapered shape.

Next, doping treatment of an inert element is selectively performed witha portion but a peripheral portion covered with a mask to form a highlydensified portion 620 on the surface of the highly thermostableplanarizing film 616. The doping treatment may be performed by iondoping or ion implantation. Typically, argon (Ar) is used as the inertelement. Distortion is given by adding an inert element having acomparatively large atomic radius, and a surface (including a side wall)is modified or highly densified, thereby preventing entry of moisture oroxygen. The inert element contained in the highly densified portion 20is set within the concentration range of from 1×10¹⁹/cm³ to 5×10²¹/cm³,typically, from 2×10¹⁹/cm³ to 2×10²¹/cm³. Note that the highlythermostable planarizing film 616 is formed to have a tapered shape sothat the inert element is doped into a surface (including a side wall)of the highly thermostable planarizing film 616. It is desirable to seta taper angle θ at more than 30° and less than 75°.

A solution component is prevented from entering the highly thermostableplanarizing film or reacting when a step using liquid (also referred toas a wet step) is performed later by adding an inert element andmodifying a surface of the highly thermostable planarizing film. Inaddition, moisture or a gas is prevented from being released from insideof the highly thermostable planarizing film when a heat treatment stepis performed later. Further, moisture or a gas is prevented from beingreleased from inside of the highly thermostable planarizing film by achange over time; consequently, reliability of a semiconductor device isimproved.

Subsequently, etching is performed using the highly thermostableplanarizing film 616 as a mask, and an exposed SiNO film or gateinsulating film containing hydrogen is selectively removed.

Next, a drain wiring and a source wiring are formed by performingetching with the use of a mask after forming a conductive film.

Then, a first electrode 623 made of a transparent conductive film, inother words, an anode (or a cathode) of an organic light emittingelement is formed. ITSO that is a transparent conductive film containingSiOx is used for the first electrode 623.

Subsequently, an SOG film obtained by application (for example, a SiOxfilm including an alkyl group) is patterned to form an insulator 629(referred to as a bank, partition wall, a barrier, a mound, or the like)covering an edge portion of the first electrode 623.

Next, a layer containing an organic compound 624 is formed byevaporation or application. Thereafter, a second electrode 625 made of atransparent conductive film, that is, a cathode (or an anode) of anorganic light emitting element is formed. ITSO that is a transparentconductive film containing SiOx is used for the second electrode 625.Subsequently, a transparent protective layer 626 is formed byevaporation, sputtering, or plasma CVD. The transparent protective layer626 is made of a silicon nitride oxide film (SiNO film) or a siliconnitride film (SiN film). The transparent protective layer 626 protectsthe second electrode 625.

Subsequently, the light emitting element is sealed by attaching asealing substrate 633 with a sealant 628. In a light emitting displaydevice, a circumference of a display portion is surrounded by thesealant and sealed with a pair of substrates. However, the interlayerinsulating film of the TFT is provided over the entire surface of thesubstrate. Therefore, when a pattern of the sealant is drawn inside acircumference edge of the interlayer insulating film, there is apossibility that moisture or an impurity might enter from a part of theinterlayer insulating film which is located outside the pattern of thesealant. Consequently, as for the circumference of the highlythermostable planarizing film used as the interlayer insulating film ofthe TFT, the sealant covers inside of the pattern of the sealant,preferably, the edge portion of the highly thermostable planarizingfilm. Note that a region surrounded by the sealant 628 is filled with atransparent filler 627.

Lastly, an FPC 632 is attached to the terminal electrode with ananisotropic conductive film 631 by a known method. A transparentconductive film is preferably used as the terminal electrode and isformed over the terminal electrode formed simultaneously with a gatewiring (FIG. 9).

According to the above steps, a pixel portion, a driver circuit, and aterminal portion are formed over one substrate.

Thus manufactured active matrix light emitting device has a structure inwhich an edge portion or an opening portion is formed to have a taperedshape in the highly thermostable planarizing film 616, typically, aninterlayer insulating film (a film to be a base film of a light emittingelement later) of a TFT in which a skeletal structure is formed by thebond of silicon (Si) and oxygen (O). Further, the active matrix lightemitting device has a structure in which distortion is given by addingan inert element having a comparatively large atomic radius, and asurface (including a side wall) is modified or highly densified, therebypreventing entry of moisture or oxygen. Accordingly, reliability of thelight emitting device is improved.

In addition, only a tapered portion in a peripheral portion of thehighly thermostable planarizing film 616 may be covered with a metalfilm or a silicon nitride film, instead of doping the tapered portionwith an impurity element.

In this embodiment, each layer (the interlayer insulating film, the baseinsulating film, the gate insulating film, the first electrode, and thesecond electrode) contains SiOx, thereby improving reliability.

Moreover, in this embodiment, each layer (the interlayer-insulatingfilm, the base insulating film, the gate insulating film, the firstelectrode, the second electrode, and the transparent protective layer)contains silicon, thereby improving each layer of adhesiveness.Adhesiveness between two layers which are in contact with each other isimproved by making the layers contain a common element (here, silicon).

[Embodiment 6]

An example of an inversely staggered TFT is described in this embodimentwith reference to FIGS. 10A and 10B. Portions other than a TFT and aterminal electrode are identical with those in FIG. 1A shown in theembodiment mode; therefore, detailed description is omitted here.

A TFT shown in FIG. 10A is a channel stop type. A base insulating film711 is formed over a substrate 710. A gate electrode 719 and a terminalelectrode 715 are simultaneously formed, and a semiconductor layer madeof an amorphous semiconductor film 714 a, an n+ layer 718, and a metallayer 717 are laminated over a gate insulating film 712. A channelstopper 714 b is formed over a portion to be a channel formation regionof the semiconductor layer 714 a. Further, source/drain electrodes 721and 722 are formed.

Further, a first electrode 723 is formed over a highly thermostableplanarizing film 716. Further, an insulator 729 is formed to cover edgeportions of the first electrode 723. Further, a layer containing anorganic compound 724 is formed over the first electrode 723. Further, asecond electrode 725 is formed over the layer containing an organiccompound 724. Further, a protective layer 726 is formed over the secondelectrode 725. Further, a light emitting element is sealed by attachinga sealing substrate 733 with a sealant 728. Note that a regionsurrounded by the sealant 728 is filled with a transparent filler 727.Further, an FPC 732 is attached to the terminal electrode 715 with ananisotropic conductive film 731 by a known method.

A TFT shown in FIG. 10B is a channel etch type. A base insulating film811 is formed over a substrate 810. A gate electrode 819 and a terminalelectrode 815 are simultaneously formed, and a semiconductor layer madeof an amorphous semiconductor film 814, an n+ layer 818, and a metallayer 817 are laminated over a gate insulating film 812. A portion to bea channel formation region of the semiconductor layer 814 is thinlyetched. Further, source/drain electrodes 821 and 822 are formed.

Further, a first electrode 823 is formed over a highly thermostableplanarizing film 816. Further, an insulator 829 is formed to cover edgeportions of the first electrode 823. Further, a layer containing anorganic compound 824 is formed over the first electrode 823. Further, asecond electrode 825 is formed over the layer containing an organiccompound 824. Further, a protective layer 826 is formed over the secondelectrode 825. Further, a light emitting element is sealed by attachinga sealing substrate 833 with a sealant 828. Note that a regionsurrounded by the sealant 728 is filled with a transparent filler 827.Further, an FPC 832 is attached to the terminal electrode 815 with ananisotropic conductive film 831 by a known method.

In addition, a semi-amorphous semiconductor film (also referred to as amicrocrystal semiconductor film) which is a semiconductor having anintermediate structure of an amorphous structure and a crystal structure(including single crystal and polycrystal) and includes a third statewhich is stable in terms of free energy, and which includes acrystalline region having a short distance order and lattice distortioncan also be used in place of the amorphous semiconductor film. Thesemi-amorphous semiconductor film is manufactured by performing glowdischarging decomposition (plasma CVD) on a silicide gas. As thesilicide gas, SiH₄, additionally, Si₂H₆, SiH₂Cl₂, SiHCl₃, SiCl₄, SiF₄,or the like can be used. The silicide gas may be diluted with H₂, or H₂and one or more of rare gas elements: He, Ar, Kr, and Ne. Dilution ratiois within the range of from 2 times to 1000 times. Pressure is roughlywithin the range of from 0.1 Pa to 133 Pa; power frequency, from 1 MHzto 120 MHz, preferably from 13 MHz to 60 MH; and substrate heatingtemperature, at most 300° C., preferably from 100° C. to 250° C. Anatmospheric constitution impurity such as oxygen, nitrogen, or carbon asan impurity element within a film is preferably at most 1×10²⁰ cm⁻¹, inparticular, oxygen concentration is at most 5×10¹⁹/cm³, preferably, atmost 1×10¹⁹/cm³. Note that field-effect mobility μ of a TFT using asemi-amorphous semiconductor film as an active layer is from 1 cm²/Vsecto 10 cm²/Vsec.

[Embodiment 7]

In this embodiment, an example of electronic devices equipped with adisplay portion is described with reference to FIGS. 11A to 11G. Anelectronic device having a light emitting device can be completed byapplying the present invention.

Generation of heat in a panel is suppressed according to the presentinvention, thereby enabling to extend a lifetime of a light emittingdevice, that is, to improve reliability of an electronic device.

Examples of electronic devices are as follows: a video camera; a digitalcamera; a goggle type display (head mounted display); a navigatingsystem; an audio reproducing device (car audio, an audio component, orthe like); a laptop personal computer; a game machine; a personaldigital assistant (a mobile computer, a cellular phone, a portable gamemachine, an electronic book, or the like); and an image reproducingdevice including a recording medium (specifically, a device capable ofprocessing data in a recording medium such as a Digital Versatile Disc(DVD) and having a display that can display the image of the data); andthe like.

FIG. 11A is a perspective view of a laptop personal computer, and FIG.11B is a perspective view thereof in a folded state. The laptop personalcomputer includes a main body 2201, a chassis 2202, display portions2203 a and 2203 b, a keyboard 2204, an external connection port 2205, apointing mouse 2206, and the like. By applying the present invention tothe display portions 2203 a and 2203 b, generation of heat in a panelcan be suppressed, and a laptop personal computer equipped with adisplay portion having high luminance with high luminous efficiency(light extraction efficiency), low power consumption, and high stabilitycan be completed.

FIG. 11C shows a television, which includes a chassis 2001, a supportingsection 2002, a display portion 2003, a video input terminal 2005, andthe like. The television includes all televisions for displayinginformation, including ones for personal computers, for TV broadcastingreception, and for advertisement. By applying the present invention tothe display portion 2003, generation of heat in a panel can besuppressed, and a television equipped with a display portion having highluminance with high luminous efficiency (light extraction efficiency),low power consumption, and high stability can be completed.

FIG. 11D shows a portable game machine, which includes a main body 2501,a display portion 2505, an operation switch 2504, and the like. Byapplying the present invention to the display portion 2505, generationof heat in a panel can be suppressed, and a portable game machineequipped with a display portion having high luminance with high luminousefficiency (light extraction efficiency), low power consumption, andhigh stability can be completed.

FIG. 11E is a perspective view of a cellular phone, and FIG. 11F is aperspective view thereof in a folded state. The cellular phone includesa main body 2701, a chassis 2702, display portions 2703 a and 2703 b, anaudio input portion 2704, an audio output portion 2705, operation keys2706, an external connection port 2707, an antenna 2708, and the like.

The cellular phone shown in FIGS. 11E and 11F is equipped with ahigh-resolution display portion 2703 a that mainly displays an image infull color and an area color display portion 2703 b that mainly displayscharacters and symbols. By applying the present invention to the displayportions 2703 a and 2703 b, generation of heat in a panel can besuppressed, and a cellular phone equipped with a display portion havinghigh luminance with high luminous efficiency (light extractionefficiency), low power consumption, and high stability can be completed.

FIG. 11G shows a display board such as an advertisement board, whichincludes a display portion 2801, a chassis 2802, a lighting portion 2803such as LED light, and the like. By applying the present invention tothe display portion 2801, generation of heat in a panel can besuppressed, and an advertisement board equipped with a display portionhaving high luminance with high luminous efficiency (light extractionefficiency), low power consumption, and high stability can be completed.

As described above, a light emitting device obtained by applying theinvention may be used for display portions of various electronicdevices. Note that a light emitting device manufactured by employing anyone of the structures of the embodiment mode, and Embodiments 1 to 6 maybe used for the electronic device of this embodiment.

Manufacturing costs can be reduced by using the same material for aninterlayer insulating film and a bank. In addition, cost reduction canbe achieved by commonality of an apparatus such as a film formationapparatus or an etching apparatus.

This application is based on Japanese Patent Application serial no.2003-322223 filed in Japan Patent Office on Sep. 12 in 2003, thecontents of which are hereby incorporated by reference.

Although the present invention has been fully described by way ofexample with reference to the accompanying drawings, it is to beunderstood that various changes and modifications will be apparent tothose skilled in the art. Therefore, unless otherwise such changes andmodifications depart from the scope of the present invention hereinafterdefined, they should be construed as being included therein.

1. A light emitting device comprising a plurality of light emitting elements having a cathode, a layer containing an organic compound, and an anode, wherein a highly thermostable planarizing film containing SiOx is formed over a substrate having an insulating surface, an anode containing SiOx and a bank containing SiOx and covering an edge portion of the anode are formed over the highly thermostable planarizing film, a layer containing an organic compound is formed over the anode, and a cathode is formed over the layer containing an organic compound.
 2. A light emitting device according to claim 1, wherein the highly thermostable planarizing film and the bank are made of the same material and are SiOx films including an alkyl group.
 3. A light emitting device according to claim 1, wherein the anode is indium tin oxide containing SiOx.
 4. A light emitting device according to claim 1, wherein a TFT using the highly thermostable planarizing film containing SiOx as an interlayer insulating film is electrically connected to the anode.
 5. A light emitting device according to claim 1, wherein the light emitting element emits red, green, blue, or white light.
 6. A light emitting device according to claim 1, wherein the light emitting device is a video camera, a digital camera, a navigation system, a personal computer, or a personal digital assistant.
 7. A light emitting device comprising a plurality of light emitting elements having a cathode, a layer containing an organic compound, and an anode, wherein light emitted from a light emitting element passes through an anode containing SiOx, a highly thermostable planarizing film containing SiOx, and a substrate having an insulating surface in a light emitting region.
 8. A light emitting device according to claim 7, wherein the light emitting element emits red, green, blue, or white light.
 9. A light emitting device according to claim 7, wherein the light emitting device is a video camera, a digital camera, a navigation system, a personal computer, or a personal digital assistant.
 10. A method for manufacturing a light emitting device including a thin film transistor and a light emitting element over a substrate having an insulating surface, comprising the steps of: forming a thin film transistor including a semiconductor layer having a source region, a drain region, and a channel formation region therebetween, a gate insulating film, and a gate electrode over a first substrate having an insulating surface; forming a highly thermostable planarizing film over an uneven shape reflected by the thin film transistor; forming an opening portion which has a tapered shape on a side face and is located over the source region or the drain region and a peripheral portion which has a tapered shape by selectively removing the highly thermostable planarizing film; forming a contact hole which reaches the source region or the drain region by selectively removing the gate insulating film; forming an electrode which reaches the source region or the drain region; forming an anode containing SiOx which is in contact with the electrode; forming a bank covering an edge portion of the anode; forming a layer containing an organic compound over the anode; forming a cathode over the layer containing an organic compound; and sealing the light emitting element by attaching a second substrate to the first substrate with a sealant surrounding a circumference of the light emitting element.
 11. A method for manufacturing a light emitting device, according to claim 10, wherein the highly thermostable planarizing film is a SiOx film including an alkyl group formed by application.
 12. A method for manufacturing a light emitting device, according to claim 10, wherein the bank is a SiOx film including an alkyl group formed by application.
 13. A method for manufacturing a light emitting device, according to claim 10, wherein the anode is formed by sputtering using a target made of indium tin oxide containing SiOx.
 14. A light emitting device comprising a plurality of light emitting elements having a cathode, a layer containing an organic compound, and an anode, wherein a highly thermostable planarizing film containing silicon is formed over a substrate having an insulating surface, an anode containing silicon and a bank covering an edge portion of the anode are formed over the highly thermostable planarizing film, a layer containing an organic compound is formed over the anode, a cathode is formed over the layer containing an organic compound, and a protective film containing silicon is formed over the cathode.
 15. A light emitting device according to claim 14, wherein a TFT using the highly thermostable planarizing film containing silicon as an interlayer insulating film is electrically connected to the anode.
 16. A light emitting device comprising a plurality of light emitting elements having a cathode, a layer containing an organic compound, and an anode, wherein a highly thermostable planarizing film containing one of silicon and silicon oxide is formed over a substrate having an insulating surface, an anode containing one of silicon and silicon oxide and a bank covering an edge portion of the anode are formed over the highly thermostable planarizing film, a layer containing an organic compound is formed over the anode, a cathode containing one of silicon and silicon oxide is formed over the layer containing an organic compound, and a protective film containing one of silicon and silicon oxide is formed over the cathode.
 17. A light emitting device according to claim 16, wherein a TFT using the highly thermostable planarizing film containing one of silicon and silicon oxide as an interlayer insulating film is electrically connected to the anode. 